The long-term objective of this research is the understanding of the role of woodrats (Neotoma sp.) As reservoirs of Leishmania in North America, and the role of associated sand flies (Lutzomysia sp.) As vectors among the woodrats and to humans. The following hypotheses will be tested: I. The southern plains woodrat (Neotoma micropus) is the reservoir of L. mexicana throughout its range, where suitable vectors are present. II. Lutzomyia anthrophora is the vector among woodrats throughout its range. III. Temporal and spatial change in prevalence of L. mexicana in N. micropus is highly correlated with change in abundance of Lu. anthrophora. IV. Beyond the geographic range of Neotoma micropus, other woodrat species replace it as reservoirs of Leishmania. V. Beyond the geographic range of Lu anthrophora, other species of Lutzomyia replace it as vectors of Leishmania. VI. Species of Lutzomyia other than Lu. anthophora are vectors to humans. Studies of the seasonal dynamics of Leishmania mexicana will continue at Medina Annex, at 7500 training annex for Lackland Air Force Base in San Antonio, Texas, where current studies have established an abundance of woodrats, sandflies and Leishmania mexicana. In addition, three research trips/year will be made to localities where Neotoma spp. Co- exists with Lutzomyia spp., including Colorado, California, Oklahoma, and Ohio. Woodrats and sand flies will be collected and screened for L. mexicana.